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    Cos 180 Degrees

    Sin, Cos, Tan, Cot of an Angle
    Function
    Angle (°)

    What is cos 180°?

    Answer

    cos 180° =
    −1

    Angle in radians: 180° = π. The point of the angle is on the x-axis: (−1, 0).

    P(cos 180°, sin 180°) = (−1, 0)

    xyOP

    P(cos 180°, sin 180°) = (−1, 0)

    Highlighted: the projection on the x-axis — cosine, x = −1.

    All four functions of 180°
    FunctionExact valueDecimal
    sin 180°00
    cos 180°−1−1
    tan 180°00
    cot 180°undefined—

    Reference angle: cos 0° = 1

    See Also

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    https://calculat.io/en/number/trigonometry/cos--180Copy
    <a href="https://calculat.io/en/number/trigonometry/cos--180">Cos 180 Degrees: Cosine of 180° on the Unit Circle</a>Copy
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    Cos 180 Degrees: Cosine of 180° on the Unit Circle. cos 180° = −1. The cosine is the x-coordinate of the point at 180° on the unit circle.
    https://calculat.io/en/number/trigonometry/cos--180/generated.jpgCopy

    Cosine of nearby angles

    Anglecos
    167°≈ −0.9744
    175°≈ −0.9962
    179°≈ −0.9998
    180°−1
    195°−(√6 + √2)/4
    198°−√(10 + 2√5)/4
    200°≈ −0.9397
    Recalculate with different values ↑

    FAQ

    What is cos 180°?

    cos 180° = −1

    Why is cos 180° equal to −1?

    The point of 180° on the unit circle is (−1, 0), and cosine is its the x-coordinate, so cos 180° = −1.

    Why does a calculator show −0.5985 for cos 180?

    The calculator is in radian mode (RAD): it takes cos 180 as the cosine of 180 radians, cos 180 rad ≈ −0.5985. Switch it to degrees (DEG): cos 180° = −1. In radians the value is never undefined: π is irrational, so a whole number of radians never lands exactly on an axis.

    See Also